True arcs on a laser - which machines can do it?

[Martin Reynolds]

Bottom line: which laser machines have the smarts to draw a circle as a single smooth line?


So I've been having trouble getting nice edges on my PETG cuts, which is always a bit of a tricky material. Replacing the linear bearings helped a lot, but I found some challenges in cutting circles and circular arcs.

What happens is, my laser shakes as it moves along these arcs. Basically, it cuts circles as a bunch of short lines, and stops at the end of each line, and restarts at the beginning of the next. This makes for vibration, and slow movement around circles.

So I went fishing and found that the driver always converts arcs to short lines.

I went further in, and managed to create a file that sends a circle to the laser.

Then, I found that the laser draws the circle as even coarser lines than the driver was sending it. GCC has pretty much promised no new firmware on these models.

So when I do find a new laser, I'm interested in one that knows how to do curves properly. Doing it right means faster movement and smoother cuts.

[Andrea Weissenseel]

As I experience the same thing with my GCC, I'm also interested in the answers. On my machine it only happens when I have to cut real slow, like thicker acrylics - on wood, paper, rubber stamps etc. the edges are smooth.

On a fair I got a butterfly, it's a 15mm acrylic, that was cut with a Sej Laser and the edges look like flame polished.

[Martin Reynolds]

Ah - yes, the edges look flame polished but also faceted.

I used the Spirit driver to make my circle. The Spirit driver will output true circles if you set the engraving resolution to 1000 dpi (I know, makes no sense but there it is).

At that setting, the laser will at least get the arc instructions.

[Neil Pabia]

My machine cuts a nice smooth arcs and has no problem with circles.

[Mark Ross]

My Epilog 36 EXT cuts perfect circles as long as the GIGO rule is followed. If the Corel file is not a single circle but a series of arcs (sometimes happens bringing in AutoCAD files) it will cut that series of arcs. As long as it is a full circle it does it with no problems.

[Rodne Gold]

I have no problems with circles with my Explorers or spirits, circles cut smoothly and dont jerk around at all , there is no facetting at all.
I do get some striations on the edges with thick acrylic , but that has nothing to do with the way the laser works but more to do with melt products.
There is a setting for curve smoothness or enhanced cutting....under the advanced tab of the driver , called enhanced vector mode, have you tried that when doing circles?

[Scott Shepherd]

but that has nothing to do with the way the laser works but more to do with melt products.

I used to agree with that comment until I was handed a sample from Trotec. It's about 3/4" thick clear acrylic and the edges look like they have been flame polished and it's straight out of the laser. Granted, it came from a high wattage machine, but none the less, the piece is crystal clear, no striations, no melt, no nothing. It's beautiful. If I can find the sample, I'll take a photo of it. We recently moved, so I'll have to look for it. I haven't seen it since the move, but prior to that, it stayed on my work table.

[Michael Hunter]

My Epilog 36 EXT cuts perfect circles as long as the GIGO rule is followed.

OK - so what is the GIGO rule?

(Probably something simple and I will feel daft for asking!)

[Rodne Gold]

gigo=garbage in , garbage out
My GCC machines are 30w, most likely now lower than that, a higher powered laser probably would cut thick stuff better and have less melt solidifying (which causes striations) My higher powered chinese machines with microsteppers cut thick stuff better.
synrad has a good article on cutting acrylic , explains the striation thing
http://www.synrad.com/e-newsletters/08_24_06.htm

[Michael Hunter]

Thanks Rodney - I now feel fully daft.

[Martin Reynolds]

My explorer is also smooth at slower speeds. Given that the driver is breaking every arc into line segments, the quality-fine-coarse-speedy settings aren't going to do much for me. Looks like some of the other manufacturers do do true arcs.